Staining Sections of Peripheral Nerves for Axis Cylinders and for Myelin Sheaths

Pieces of mammalian nerves 1 to 2 cm. long were placed under moderate tension and fixed 24–48 hours in: picric acid, saturated aqueous, 90 ml.; formalin, 10 ml.; and trichloracetic acid, 25% aqueous, 2 ml. They were washed in water, cut in two and one end stained with 0.04–0.06% osmic acid solution, while the other was dehydrated, embedded in paraffin, and mounted sections from it stained with protargol. The fixing solution used was selected from a number of combinations of acidified picro-formalin as the one most likely to give satisfactory results when followed by both silver and osmic acid. The use of osmic acid solutions of less than 0.1% concentration avoided the overstaining of myelin sheaths seen frequently when stronger solutions were used with material that had been fixed previously. Protargol, 0.5% solution with fast green FCF added to make 0.05% dye in the final concentration, was used to impregnate sections for axis cylinders. Reduction and toning were done as in Bodian's method.     

Bioaccumulation of Key Metals and Other Contaminants by Seaweeds from the Egyptian Mediterranean Sea Coast in Relation to Human Health Risk

This study examined the bioaccumulation of key metals and other contaminants (SO₄, F, Na, K, Ca, Mg, P, Si, Fe, Mn, Zn, Ni, Co, Cu, and Cd) by seaweeds from the Egyptian Mediterranean Sea coast and their risk to human health. Bioaccumulation factor calculations indicated that S, F, Na, K, Zn, Cu, and Cd had high seaweed uptake and this referred to the potential pollution of the coastal area. Multivariate analysis of the studied contaminants confirmed the bioaccumulation factor results as well as the physiological processes in seaweeds. Human health risk assessment of F, Mn, Zn, Ni, Cu, and Cd was conducted using hazard quotient (HQ) and incremental lifetime cancer risk (ILCR) analyses. The carcinogenic assessment of sediments and ingestion of seaweeds using ILCR calculations revealed that Mn, Ni, and Cd in sediments and F and Zn in seaweeds require remedial action in order to reduce their human health risks. Additionally, HQ calculations for the contaminants in seaweeds and reference to toxicological references values from different agencies revealed that F and Co present high human health risk effects. Consequently, the potential public health risks from dietary exposure to hazardous contaminants in seaweeds must be continually subjected to research, regulation, and debate.     

Assessment on Pollution by Heavy Metals and Arsenic Based on Surficial and Core Sediments in the Cam River Mouth,Haiphong Province,Vietnam

The Cam River mouth (Haiphong Province) is one of the main river mouths of the Red River System, which is one of the most important water resources in Northern Vietnam. Over the past 50 years, the strong socio-economic development in the area has caused a considerable contamination with heavy metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) and arsenic. In this study, the vertical and horizontal distributions of heavy metals and arsenic in sediments from the Cam River mouth were investigated. In addition, the history, origin, and degree of contamination were assessed. Normalized (with respect to Al) heavy metal and arsenic concentrations in sediment cores and absolute dates obtained from the ¹³⁷Cs analysis were used to reconstruct the pollution history of the river mouth. As, Cu, Mn, Pb, and Zn concentrations increase rapidly by approximately two times or more from 1954 to 1975, and then remain nearly unchanged from 1975 until 2008, whereas Co, Cr, and Ni concentrations slightly increase from 1954 until 2008. In addition, background values for heavy metals and arsenic have also been determined with regard to the period before 1954. In the study area, Co, Cr, Cu, Ni, Mn, and Zn are evaluated as minorly enriched, whereas As and Pb are classified as moderately enriched. Generally, the anthropogenic activities in the Haiphong harbor and industrial zone locally contribute to the contamination by heavy metals and arsenic in the Cam River mouth.     

Application of Semipermeable Membrane Devices (SPMDs) and Benthic Mussels to Evaluate the Bioavailability of Sediment-associated DDTs

Bioavailability of dichlorodiphenyltrichloroethanes (DDTs) in surface sediments was evaluated with semipermeable membrane devices (SPMDs) and two different sediment-dwelling benthic mussels, Bellamya aeruginosa (B. aeruginosa) and Corbicula fluminea (C. fluminea). After 28d laboratory exposure, the positive correlations of DDT concentrations between both SPMDs and benthic mussels with sediments documented that the bioavailability of DDTs was mainly affected by surrounding sediments, while the observed differences of DDT concentrations and congener proportions between B. aeruginosa and C. fluminea were due to the specific physiological characteristics of organisms and different physico-chemical properties of contaminants. Comparisons between SPMDs and benthic mussels showed higher values of biota-sediment accumulation factors (BSAF, 0.63-3.61 for B. aeruginosa and 2.19-17.08 for C. fluminea) than device accumulation factors (DAF, 1.00-1.74). This indicated that living organisms bioaccumulated much more DDTs from sediments than SPMDs due to the different exposure and uptake routes. Strong positive associations between DDTs in SPMDs and benthic mussels indicated SPMDs could mimic the bioaccumulation of DDTs, especially in C. fluminea. However, given the distinct differences observed for both concentrations and congener proportions of DDTs in SPMDs and B. aeruginosa, future study should be directed to develop reliable models with various sediment-dwelling organisms before SPMDs are routinely used in field study.     

Detrital diversity influences estuarine ecosystem performance

Global losses of seagrasses and mangroves, eutrophication‐driven increases in ephemeral algae, and macrophyte invasions have impacted estuarine detrital resources. To understand the implications of these changes on benthic ecosystem processes, we tested the hypotheses that detrital source richness, mix identity, and biomass influence benthic primary production, metabolism, and nutrient fluxes. On an estuarine muddy sandflat, we manipulated the availability of eight detrital sources, including mangrove, seagrass, and invasive and native algal species that have undergone substantial changes in distribution. Mixes of these detrital sources were randomly assigned to one of 12 treatments and dried detrital material was added to seventy‐two 0.25 m² plots (n = 6 plots). The treatments included combinations of either two or four detrital sources and high (60 g) or low (40 g) levels of enrichments. After 2 months, the dark, light, and net uptake of NH₄⁺, dissolved inorganic nitrogen, and the dark efflux of dissolved organic nitrogen were each significantly influenced by the identity of detrital mixes, rather than detrital source richness or biomass. However, gross and net primary productivity, average oxygen flux, and net NO_X and dissolved inorganic phosphorous fluxes were significantly greater in treatments with low than with high detrital source richness. These results demonstrate that changes in detrital source richness and mix identity may be important drivers of estuarine ecosystem performance. Continued impacts to estuarine macrophytes may, therefore, further alter detritus‐fueled productivity and processes in estuaries. Specific tests that address predicted future changes to detrital resources are required to determine the consequences of this significant environmental problem.     

Complete genome sequence of Desulfocapsa sulfexigens,a marine deltaproteobacterium specialized in disproportionating inorganic sulfur compounds

Desulfocapsa sulfexigens SB164P1 (DSM 10523) belongs to the deltaproteobacterial family Desulfobulbaceae and is one of two validly described members of its genus. This strain was selected for genome sequencing, because it is the first marine bacterium reported to thrive on the disproportionation of elemental sulfur, a process with a unresolved enzymatic pathway in which elemental sulfur serves both as electron donor and electron acceptor. Furthermore, in contrast to its phylogenetically closest relatives, which are dissimilatory sulfate-reducers, D. sulfexigens is unable to grow by sulfate reduction and appears metabolically specialized in growing by disproportionating elemental sulfur, sulfite or thiosulfate with CO₂ as the sole carbon source. The genome of D. sulfexigens contains the set of genes that is required for nitrogen fixation. In an acetylene assay it could be shown that the strain reduces acetylene to ethylene, which is indicative for N-fixation. The circular chromosome of D. sulfexigens SB164P1 comprises 3,986,761 bp and harbors 3,551 protein-coding genes of which 78% have a predicted function based on auto-annotation. The chromosome furthermore encodes 46 tRNA genes and 3 rRNA operons.     

AN ASSESSMENT OF THE POTENTIAL IMPACT OF ALIEN INVASIVE VEGETATION ON THE GEOMORPHOLOGY OF RIVER CHANNELS IN SOUTH AFRICA

Summary

Invasion of the riparian zone by alien vegetation is recognised as a serious problem in many areas of South Africa. Vegetation is a dynamic component of river channels. It is an important control variable affecting channel form whereas the flow and sediment regime influences vegetation growth. Wherever alien vegetation invades the riparian zone it can be expected that there will be some impact on the physical structure of the riparian habitat. This paper reviews the effect of riparian vegetation on channel processes and channel form and discusses the implications of the invasion of riparian zones by alien vegetation. Woody species in particular are seen as having a significant potential for inducing channel modification, whilst their removal could lead to significant channel instability and mobilisation of sediment. The need for further research into the impact of alien vegetation on the geomorphology of South African river channels is stressed.     

Importance of plant integrity in crop research,breeding, and production

Plant integrity looks like a “very easy and expanded topic,” but the reality is totally different. Thanks to the very high specialization of scientists, we are losing a holistic view of plants and are making mistakes in our research due to this drawback. It is necessary to sense a plant in their whole complexity—in both roots and shoot, as well as throughout their life cycles. Only such an integrated approach can allow us to reach correct interpretations of our experimental results.     

西藏及其东南地区被子植物与其不同生活型的果实类型分析

统计了分布在西藏自治区的被子植物及各生活型果实的类型及比例,并与藏东南地区做了比较。结果如下,西藏自治区果实以蒴果为主(占37.74%),其次为瘦果、坚果、浆果等;干果的比例远远大于肉果;不同生活型的果实类型谱差异较大,乔木中核果的比例最高,藤本中浆果比例最高,灌木中瘦果比例最高,草本中蒴果占优势;4个生活型中,肉果的比例乔木为最高,其次为藤本、灌木、草本。藏东南地区植物的果实类型也以蒴果为主,其次为瘦果、浆果、核果等;藏东南乔木中核果比例最高,藤本中浆果比例最高,灌木和草本植物以蒴果占优势;乔木肉果的比例最高,其次为藤本、灌木、草本。藏东南肉果比例大于全藏区,而干果比例则相反。果实类型的这些性状特征与各自的环境相适应,是植物长期适应自然环境的进化结果,该研究对于理解植物果实对生态环境的长期适应进化具有一定的意义。     

Influences of seasons and dietary composition on diurnal raptor habitat use in Chembe Bird Sanctuary,Zambia: Implications for conservation

Diurnal raptor habitat use has conservation implications due to environmental and anthropogenic interactions. Three tree-nesting diurnal raptors, black kites (Milvus milvus), steppe buzzards (Buteo vulpinus) and African fish eagles (Haliaeetus vocifer), were studied from December 2016 to October 2017. The objective was to determine factors influencing diurnal raptor habitat selection and use in and around Chembe Bird Sanctuary of Kalulushi district, Zambia. We surveyed for birds in ten randomly selected 200 × 200 m sample plots in each of the five stratified sampling units (miombo woodland, grasslands, human settlements, Lake Chembe and marsh). Seasons and dietary composition variably influenced the distribution, habitat selection and use by raptors. The three raptors devised a suit of behaviours to curtail challenges associated with seasonal food and water availability, and anthropogenic disturbances. There is a need to promote multi-stakeholder engagement and involvement in raptor conservation.